RFR (S): 8212911: Unify and micro-optimize handling of non-in-collection set references in oop closures

[Thomas Schatzl]

Hi all,

On Wed, 2018-10-24 at 13:36 +0200, Thomas Schatzl wrote:
> Hi all,
> 
>   can I have reviews for this small change that does some minor
> cleanup and micro-optimization of our main g1 stw/concurrent gc
> closures?
> 
> [...]
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8212911
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8212911/webrev/
> Testing:
> hs-tier1-3, several hs-tier1-5 runs with other changes, benchmark
> suite etc.

  Stefan pointed out that _from_in_young is only used in
G1ScanEvacuatedObjClosure any more, so it could be moved from
G1ScanClosureBase.

Also we brainstormed a bit about the name of _from_in_young, and agreed
on changing this to _scanning_in_young.

New webrevs:
http://cr.openjdk.java.net/~tschatzl/8212911/webrev.1 (full)
http://cr.openjdk.java.net/~tschatzl/8212911/webrev.0_to_1 (diff)

Thanks,
  Thomas